1. Field of the Invention
The present invention relates to an ink-jet recording ink and an image-forming method, in particular to an ink-jet recording ink comprising an oil-soluble dye as the coloring ingredient, and an image-forming method using the ink.
2. Description of the Related Art
Concomitant with the spread of computers in recent years, ink-jet printers have been widely used for printing on paper, film and cloth, not only in offices but also in homes. As inks for ink-jet recording, an oil-based ink, an aqueous ink and a solid ink are known, and in particular, the aqueous ink is advantageous in terms of easiness of production, handling, odor and safety, and hence is mainly used.
Most aqueous inks make use of water-soluble dyes dissolved in a molecular state and thus have the merits of high transparency and high color density. However, because the dyes are water-soluble, aqueous inks suffer from the disadvantages of poor water resistance and easily bleeding when printing on paper thus leading to a serious deterioration in the quality of printing and poor light resistance. A marked deterioration in image storability also results from the influence of oxidizing gases (SOx, NOx, ozone etc.) on a recording paper (hereinafter referred to as photographic paper) provided with an ink-receiving layer thereon containing porous inorganic fine particles.
In order to solve the problems described above, aqueous inks using a pigment or a disperse dye are proposed (see, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 56-157468, 4-18468, 10-110126 and 10-195355). These aqueous inks have improved in terms of water resistance to a certain degree, but they cannot yet be said to have reached a satisfactory level. Aqueous inks also have a problem of poor dispersion stability of the pigment or the disperse dye therein, and clogging has tended to occur frequently at an ink discharge opening. Further, there have also been the problems that the ink using the pigment or the disperse dye is not easily absorbed by photographic paper, and that in consequence the pigment or the dye is easily removed from the surface when rubbed by hand. Incidentally, a disperse dye means an oil-soluble dye dispersed as oil droplets in water.
A method of incorporating a dye into dispersed particles of urethane or polyester has also been proposed (see, for example, JP-A Nos. 58-45272, 6-340835, 7-268254, 7-268257 and 7-268260). However, the ink for an ink-jet obtained by this method is poor in color tone and also inferior in terms of color reproducibility and discoloration properties. Further, the ink used in printing on photographic paper is poor in abrasion resistance when rubbed with an eraser.
Also, a technique has been disclosed which uses a water-soluble dye system and forms a vivid image without generating spots or irregular dots (see, for example, JP-A No. 10-95942).